A related art battery pack is configured such that it is detachably attached to a grip portion of an electric tool or to a battery charger, and when the battery pack is attached to the equipment, positive and negative terminals of the battery pack are contact the terminals of the equipment.
JP 2008-103144 A discloses a structure for sliding and a battery pack relative to a mounting portion of an electric tool to attached the battery pack to the electric tool. The battery pack includes an engaging hook configured to engage with the mounting portion of the electric tool to attach the battery pack to the mounting portion.
The battery pack includes engagement releasing buttons on respective sides thereof. To detach the battery pack, the engagement releasing buttons are pushed into the battery pack to move the engagement hook in an engagement releasing direction. Each of the engagement releasing buttons has an inclined inner face contacting a receiving portion of the engaging hook. When the engagement releasing buttons are pushed in, the receiving portion of the engaging hook slides on the inner faces of the engagement releasing buttons so that the engaging hook is moved in the engagement releasing direction.
However, in a work site, dust enters the inside of the battery pack, and the dust may adhere to the sliding faces of the engagement releasing buttons and the engaging hook. When the engagement releasing operations are carried out with the dust adhered to the sliding faces, the sliding faces are roughened due to the interposed dust, resulting in an increase in frictional resistance and deterioration of operability. In the worst case, the engagement releasing operation cannot be carried out.